The optical recording media are in widespread use, generally due to its superior characteristics such as large recording capacities, non-contact recording or reproduction, and the like. In the write-once optical discs such as WORM, CD-R, DVD±R, and the like, recording is carried out by focusing the laser light on a minute area of the recording layer to change properties of the optical recording layer, while reproduction is performed based on a difference in intensities of light reflected from the recorded area and non-recorded area.
Presently, in the optical discs mentioned above, the wavelength of a semiconductor laser used for recording and reproduction is between 750 and 830 nm for CD-R and between 620 and 690 nm for DVD-R. However, in order to realize further increase in capacity, an optical disc which uses short-wavelength laser light is being explored. For example, one which uses light of wavelength between 380 and 420 nm as the recording light is under study.
In an optical recording medium for the short-wavelength recording light, various compounds are used to form the optical recording layer. For example, Patent Document 1 reports an optical information recording medium comprising a metal complex containing a chalcone type compound as a ligand and Patent Document 2 reports an optical recording medium comprising a specific chalcone type compound. However, these compounds used for an optical recording medium did not necessarily have absorption wavelength characteristics suitable for an optical recording material used to form an optical recording layer.
Further, Patent Document 3 reports a light absorber for clothing material and, as an example of a compound used suitably as the light absorber, an organic dye compound having a chalcone type structure is cited. However, there is no description nor suggestion that the organic dye compound having the chalcone type structure may be used as an optical recording material.
Patent Document No. 1: Japanese Patent Laid-Open Publication No. 2003-11511
Patent Document No. 2: Japanese Patent Laid-Open Publication No. 2004-306306
Patent Document No. 3: Japanese Patent Laid-Open Publication No. 2000-328039